This invention relates to a magnetic spring clutch which has an improved magnetic flux path which provides for a more reliable operation of the clutch and which also has a simplified, low-cost construction.
This invention belongs to that class of clutches which has a normally, continuously-running input hub which is coupled, when the clutch is activated, to a normally, stationary, output hub. The input and output hubs are axially aligned with each other, and the clutch includes a helical spring having one end which is secured to one of the hubs and having some of the turns of the spring surrounding the remaining hub. Various means are used to cause the free end of the spring to tighten on the associated hub to provide a driving connection between the input and output hubs whenever the clutch is energized.
Some of the means for causing a clutch spring to tighten on the associated hub of a magnetic spring clutch which are representative of the prior art are shown in the following U.S. Pat. Nos.
2,976,976 which issued Mar. 28, 1961; PA1 3,349,880 which issued Oct. 31, 1967; PA1 3,414,100 which issued Dec. 3, 1968; PA1 3,684,068 which issued Aug. 15, 1972; and PA1 3,735,847 which issued May 29, 1973.
In general, the clutches shown in the above named patents utilize intermediate moveable members (like a brake shoe for example) which are acted upon by the magnetic force of a coil when the coil is energized. The intermediate member, in moving, acts upon the helical spring of the clutch causing the spring to tighten on the output hub of the clutch to provide a driving coupling between the input and output hubs.
In contrast with the above, the magnetic spring clutch of this invention does not utilize an intermediate moveable member which is magnetically actuated to act upon the clutch spring, causing it to tighten on the output hub of the clutch. This invention utilizes a floating magnetic ring (to be later defined herein) which is secured to the output hub of the clutch, and also uses a construction which concentrates the magnetic flux of its associated coil means along the length of the helical spring itself and the floating magnetic ring to provide for a reliable, quick-acting clutch of simple construction. The assignee of this application has manufactured for several years a magnetic spring clutch without an intermediate moveable member; however, this prior art clutch does not have the floating magnetic ring, the improved magnetic flux pattern, or the simplified construction of the present invention.